Hi!
Normally, a visual style is only applied on the session you use, it has no incidence on other users sessions.
Although, I haven't updated the deviation of this theme since ages. So, I don't advise to change any .dll file, it might screw your computer up!
haha, LaBerlue... in my language, "avoir la berlue" means "to have a wrong idea about something" or "to have hallucinations" (sorry for my bad English)
Have a nice end of the day!